There is disclosed in U.S. Pat. Nos. 4,695,712 and 4,717,814 a quite thin, strap-like device that is a flexible heater employed to solder braids of electrical conductors or metal junctions to one another. These prior art straps have been sold, by the assignee cf the present invention, under the trademark "SOLDER STRAP" for about five years. The devices are comprised of a centrally located return buss, a high mu material located on one side and insulated from the return buss and an outer sheath. The sheath on the side of the return bus remote from the high mu material is transversely slotted to render the strap flexible, so that it may be wrapped about a pipe or braid.
The heater is usually provided with a latch and is adapted to cooperate with a tool that both cinches the strap and provides a constant current thereto. The heater extends along a length of the strap remote from the end that cooperates with the tool for only a distance necessary to surround the pipe or braid. A length of strap that extends from the tool to the heater region serves as a transmission line and does not include high mu material. This length of sheath is however transversely slotted along its entire length in order to impart flexibility. Also as the strap is cinched during use, the transmission line section folds easily upon itself without kinking, which might internally short out the strap. The currently available straps are limited, in the power that can be delivered to a load, to about 250 watts. Demands have developed for a higher wattage strap, but one in which the physical dimensions remain unchanged, and which operates at the same temperature.
Further, recent developments have indicated a potential need for a strap that operates at much higher temperatures, specifically braze temperatures. The present strap operates at solder temperatures of about 350.degree. C. to 450.degree. C., while braze temperatures are in the 700.degree. C. to 850.degree. C. range.